1. Field of the Invention
The present invention relates to an image forming apparatus having a communication function, such as a facsimile machine or a multi-function machine.
2. Description of the Related Art
Conventionally, there are various types of image forming device having a communication function.
Japanese Laid-Open Patent Application No. 8-130595 discloses an image forming device having a communication function, in which operational history data is stored. Changes in the operational state of the image forming device are stored as the operation history data. With this image forming device, the user can detect whether the operational state has been shifted to a power-saving mode, by accessing the changes in the operational state in the stored operational history data. Such configuration of the operational history data provides the user with the reliability of the image forming device.
Japanese Laid-Open Patent Application No. 9-307672 discloses an image forming device having a communication function. In this image forming device, it is set in a power-saving mode at a suitable timing according to the operation situation and the facsimile receiving situation. A time interval between an end of the image forming operation or an end of the facsimile receiving procedure and a start of automatic power-saving mode setting is controlled based on the operation history data and facsimile receiving history data.
Japanese Laid-Open Patent Application No. 10-173840 discloses an image forming device having a communication function. In this image forming device, a plurality of component units in which the supply/stop of source power to the component units is performed are grouped into a set of blocks. A power-saving unit is provided for each of such blocks. At the time of a start of power supplying, the power-saving unit for a specific block is operated with a time delay, while the power-saving units for other blocks are operated without delay. According to the conventional image forming device, it is possible to control the useless power consumption at the time of the power supplying start.
In recent years, many image forming devices are equipped with the low-power setting function that reduces the power consumption in a standby state low as much as possible. For example, two conceivable methods that attain the energy saving are as follows.
(1) The power source that supplies electric power to the electrical components, such as a fixing heater and a drive motor, is turned off.
(2) The clock signal of the CPU is set at a low speed and a sleep command is issued to the CPU so that the CPU is set in the low-power state. Hereinafter, this state will be called the sleep mode.
However, in the conventional power-saving method, when there is a standby file, such as a time-specified transmission file the transmission time of which is specified, the CPU at that time is not able to be switched to the sleep mode because it must perform the transmission of the file at the specified time. Therefore, the conventional image forming device is capable of changing to the low power state only in the case of the above (1). When there is the standby file, the conventional image forming device has the problem in that the larger the difference between the current time and the start time of transmission specified by the standby file is, the larger the power consumption becomes.
Generally, the following files are stored in a facsimile system as information treated as the standby files.
(1) The time-specified transmission files with which the time of the transmission is specified.
(2) The time-specified polling transmission standby files that are waiting to be transmitted by the polling at the time specified therein.
(3) The retransmission files that are waiting to be retransmitted because of the occurrence of an error or during the conversation.
(4) The charging management reports with which the total of the communication charges is output and transmitted at a fixed time.
Conventionally, when the time-specified transmission files are stored, it has been impossible for the conventional image forming device to switch the operating state of the CPU to the sleep mode because the CPU must perform the transmission of such files at the specified time. Therefore, it is difficult that the conventional image forming device effectively provide power saving when the time-specified transmission files are stored.